The Cornell University Center for Hospitality Research, in a research snapshot from August, reported that flash-sale travel deals generated an estimated $19.9 million in revenue, 11 percent of the revenue across the entire flash-sale industry.

Flash sales advertise a hotel stay, restaurant meal or other product or service for a limited time at deep discounts (ranging from 15 to 75 percent).

The deals have gained popularity because they offer advantages to everyone: consumers, businesses and e-marketers (the deal makers).

Typically, the buyer purchases an online voucher or coupon to try out new hotel or dining experiences they might not ordinarily be able to afford or may not have known about.

Many sites display enticing countdown clocks showing the hours and minutes left to take advantage of the offer.

Hotels are able to offload rooms at times when beds would otherwise remain empty. Similarly, restaurant deals usually are limited to slow sales periods.

The biggest advantage to advertisers: The publicity exposes hotels or restaurants to a wide audience, beyond those who actually click and purchase during the sale period.

The deal-makers get a cut of the profits.

Flash sales can yield substantial savings, but as always, buyers need to be savvy consumers. Here are 10 tips to avoid the land mines:

1. Resist impulse purchases. These ads are designed to connect with your inner shopper, and they do it well. Beautiful photography, rock-bottom prices and effusive recommendations on social media make it easy to buy something you don't need or can't use.

2. Don't believe everything you read. Check out the actual website of the hotel or resort, and compare prices before you make a purchase. Glance at the restaurant menu online to see how the deal compares with usual pricing. Check out actual user reviews.

3. Read the fine print. Many deals are nonrefundable, so read all terms and conditions carefully, especially involving cancellations and refunds. Determine whether the offer is for a fixed date or flexible period and whether taxes, fees, gratuities, parking and/or other incidental expenses are included.

4. Note the expiration date. Make sure you are able to use the voucher before it expires. (Applicable state laws vary, but many vouchers purchased online retain their cash value for as long as five years, even if the deal that inspired the purchase has expired.)

5. See what forms of payment are accepted. Most sites accept credit cards or PayPal. Make sure you are shopping on a trustworthy site using an encrypted network connection.

6. Determine how to contact the vendor with questions or complaints. Make sure there is a convenient way to report and resolve problems in obtaining or redeeming your purchase. Many sites have "concierges" available by phone or email for troubleshooting.

7. Read the privacy policy. Flash-sale sites have access to your personal data. Make sure you know how it may be used.

8. Understand redemption policies. Carefully read the redemption instructions. For example, restaurants may require you to show the voucher to your server before ordering. Keep a print copy and electronic backup in case you need it.

9. If you can't go, check whether the offer is refundable or transferable. Stuff happens.

10. Provide feedback. Especially if you have a problem redeeming a coupon or are disappointed with the quality of an experience, let the flash site know. They want your continued business and often will find a way to keep you as a satisfied customer.